Trying to resurrect a Zoom 508 Delay

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Trying to resurrect a Zoom 508 Delay

Postby flood » 06 Apr 2013, 05:53

One of my first pedals and also my favourite through my student days, my Zoom 508, has been somewhat dead for a while now. I love delay, so I did get myself a couple of other cheap pedals and just recently a TC Flashback, but I would love to resurrect (and rehouse) this thing. I'm convinced that the problem is in the power supply and I would love it if someone can simply point me in the right direction.

Very simply put, the LEDs and alphanumeric display light up when I connect the power supply, but only for an instant - they're out again almost immediately. I have a feeling the LEDs are still on, but are simply too faint to know for sure.

Here's a video: http://www.youtube.com/watch?v=AQPD9hOsuNI

Thinking it could be the 220 uF 16V reservoir cap after the diodes, I swapped it out to no avail; there's a weird voltage regulator after this cap with 4 pins labelled C2255 M702L, still trying to find a definitive datasheet for that.

In any case, I'd be grateful if someone could chime in on this! If I can get it working again, I'd want to rehouse it in an aluminum enclosure with off-board jacks, momentary stomp switches and true bypass as well, give this thing an extended lease on life. :) Thanks for looking!
In the interest of full disclosure, I am Animal Factory Amplification.
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Re: Trying to resurrect a Zoom 508 Delay

Postby tasteless » 06 Apr 2013, 17:48

Datasheets for the other components might offer a few clues ?
Or , Maybe there's some other pedal that uses the same delay chip.
Delay line datasheets will often have an example cct in them , Anything similar that might allow You to deduce the regulator voltage.
From there You could start hunting through the MOUSER ( or similar ) catalogue for a regulator with the same physical dimensions etc..
I'm afraid that's the best I can offer at the moment.
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Re: Trying to resurrect a Zoom 508 Delay

Postby flood » 08 Apr 2013, 07:09

Thanks, I'm looking out for the components... unfortunately, I think they were used almost only in Japan. The delay chip is a proprietary Zoom DSP. There's an SMD voltage reference IC marked NJU7201, unfortunately missing the vital suffix that tells you what the output voltage should be.

I'm also wondering if it's simply a pedal that needs more current than others, and isn't getting enough... I doubt that though, because it refuses to work with other beefier power supplies too. The voltage across the LEDs is a constant 2.3V, i'm guessing these are low-power garden variety types that shouldn't be so dark at just under 3V, unless they aren't getting enough current. Or there's a short somewhere.

Will keep looking, am not going to give up on this one so easily...
In the interest of full disclosure, I am Animal Factory Amplification.
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Re: Trying to resurrect a Zoom 508 Delay

Postby tasteless » 08 Apr 2013, 12:07

I took a peek inside a friends 505 - Yep , Same regulator.
Measured 9.26 , 4.99, Gnd , 5.01 from left to right with the board face up ( the side with the display ).
I would have guessed that DSP stuff would require 5V.
I can probably borrow it , If You need to know more - I reckon it's only the software that would differ.
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Re: Trying to resurrect a Zoom 508 Delay

Postby flood » 09 Apr 2013, 07:00

tasteless, thanks a TON for your efforts and chiming in with that post! it gives me a good starting point, the voltage that should be 9V is showing 1V so i'm guessing it's getting dropped either before or the regulator input is shorting to ground somewhere... or the regulator itself is shot.

i also found the datasheet for the part, it's attached to this post. will have to track it down...
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Re: Trying to resurrect a Zoom 508 Delay

Postby tasteless » 09 Apr 2013, 15:09

Hey , It was just a timely coincidence that I found myself in a house with a 505 ( and..happened to be packing a multi-meter ).
I'm looking over a couple of amps for the owner , He said can drop it around later in the week.
Good job finding the regulator - That's the hard part over with.
I've only briefly skimmed through the pdf - Curious device indeed !
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